symbiont

[sĭm′bē-ŏnt′, -bī-]symbiote(sĭm′bē-ōt′, -bī-)

An organism in a symbiotic relationship. In cases in which a distinction is made between two interacting organisms, the symbiont is the smaller of the two and is always a beneficiary in the relationship, while the larger organism is the host and may or may not derive a benefit. See also hostparasite.